c) A system has the open-loop transfer function $G_1(s)H_1(s) = \frac{K_1(s+2)(s+4)}{s^3}$.
Determine, with the aid of a sketch of the root locus for the system, the
range of the value of the gain constant $K_1$, for which the system is stable
in closed-loop. The root locus has a break point at $s = -9.4$